Overview

Brief Summary

Egretta caerulea

A medium-sized (24 inches) wader, the Little Blue Heron is most easily identified by its size, blue body, purplish neck, and gray bill tipped with black. Other field marks include dull yellow-green legs, dark eyes, and (unlike most herons) a lack of ornamental breeding plumes during the breeding season. Immature birds are all white, but may be separated from other white herons and egrets by their yellow legs and gray bill. Male and female Little Blue Herons are similar to one another in all seasons. The Little Blue Heron breeds in the southeastern United States and along the Atlantic Coast of the U.S.north to Maine. Birds breeding in the interior spend the winter from southern California south to Panama. Coastal populations south of New Jersey, as well as those in the West Indies, are non-migratory. Little Blue Herons breed in colonies along shallow bodies of water, including marshes, lakes, and estuaries. Nests are usually built in the branches of trees above the water. Wintering birds generally utilize similar habitats as in summer. Little Blue Herons primarily eat small fish. Little Blue Herons may be best observed wading in shallow water, where they may be seen plunging their bills into the water to catch fish. It is also possible to see Little Blue Herons at their rookeries, especially when they return to roost at sunset, or while flying with their feet extended and their necks pulled in. Little Blue Herons are primarily active during the day.

Characteristics

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Distribution

The Little Blue Heron is found along the Atlantic coast from Massachusetts to Florida, but is most abundant along the Gulf of Mexico. It also nests in the West Indies, and along both Mexican coasts through Central America and into South America. Its range can also extend into the Amazon Basin, the Caribbean, and the more northern regions of North America. (Riegner 1998)

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Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) BREEDS: southern California (casually, since 1979), southern Sonora, southeastern New Mexico, northern Texas, central Oklahoma, central Kansas, southwestern Kentucky, southern Georgia, and Atlantic coast north to Maine, south along both coasts of Mexico and Middle America, to the West Indies and South America (Colombia, Venezuela, and Guianas west of Andes to central Peru and east of Andes to eastern Peru, central Brazil, and Uruguay; sometimes in central Minnesota. See Spendelow and Patton (1988) for information on distribution and abundance of coastal U.S. breeding populations. NORTHERN WINTER: north to southern Baja California, southern Sonora, Gulf Coast, and Virginia, south through most of the breeding range. In the U.S., the highest winter densities occur in southern Louisiana bayous, around the mouth of the Mississippi River, especially the Delta NWR, and to a much lesser extent in Florida (Root 1988). Wanders irregularly outside usual range, especially after breeding. Accidental or casual in Hawaii.

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Physical Description

Morphology

The Little Blue Heron is a small, dark bird that ranges from 63-74 centimeters in length. It can have a wingspread of up to 1.04 meters. The sexes look similar, but the young look very different from the adults. An adult can be recognized by its purple-maroon head and neck. The rest of the plumage is slate gray. The long neck is usually held in an "S" shaped curve while the bird is at rest or in flight. The heron's long, slender bill curves slightly downward, and is also dark gray but has a black tip. The eyes are yellow and the legs and feet are dark. The young are unlike any other heron because they have all white body plumage. They have a blue bill with a black tip and dull green legs. They stay white through their first summer, fall, and into winter, but start molting in February into the dark color of an adult. (Terres 1980; Tarski 2001)

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Ecology

Habitat

Although Egretta caerulea often lives near saltwater, it is mainly an inland bird. They prefer freshwater areas such as ponds, lakes, marshes, swamps, and lagoons, but also sometimes occupy flooded and dry grasslands, or marine coastlines. (Riegner 1998, Terres 1980, Tarski 2001)

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Migration

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: Yes. At least some populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: Yes. At least some populations of this species make annual migrations of over 200 km.

Northern populations are migratory. Individuals banded in North America have been recorded in Colombia November-March (Hilty and Brown 1986).

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Trophic Strategy

Egretta caerulea feed mainly during the daylight hours. They are carnivorous, with their diet consisting of fish, frogs, lizards, snakes, turtles, and crustaceans such as fiddler crabs, crayfish and shrimp. They also eat aquatic insects and spiders. When swamps and marshes become dry, they live on grasshhoppers, crickets, beetles and other grassland insects.

The Little Blue Heron's long legs enable it to wade into the water, where it walks slowly along an area in order to locate prey, often retracing its steps or standing motionless. They sometimes rake the ground with their foot to disturb prey into movement and stretch their long necks to peer into the water. Their long beak is used to jab and eat the prey. Extensive studies found the heron's prey capture success rate to be about 60 percent. (Terres 1980, Riegner 1998)

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Comments: Eats various small aquatic animals, also grassland insects, especially when marshes and swamps dry; generally forages ashore or in mud or shallow water, seldom feeds in salt water (Palmer 1962).

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Reproduction

The pale, blue-green eggs of the Little Blue Heron are laid in April. They can lay from 3-5 eggs, but on average lay 4-5. This process takes 5-8 days, with one egg being laid every other day. Both sexes incubate the eggs until they hatch in 22-24 days, and then quickly remove the eggshells from the nest. It may take about 5 days for all of the chicks to emerge. Although the young can raise their heads, they spend most of their time lying on the nest floor. Both parents feed them by dropping food into the nest and later placing it directly into the chicks' mouths. In about 3 weeks, the young are ready to leave the nest for short trips along surrounding branches. When they are 30 days old, they are able to fly and periodically leave the nest area. Soon after, at 42-49 days, the young are on their own. Little Blue Herons can breed when they are one year old. They have been recorded as living more than 7 years in the wild. (Riegner 1998, Terres 1980, Katusic 1998)

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Conservation

Conservation Status

The major problem facing these birds is the loss of their wetland habitats. Little Blue Herons need clean, undisturbed wetlands for feeding and breeding. Colonies are being lost because of clear cutting of forests, and draining of ponds, lakes, and wetlands. The use of pesticides has also caused eggshell thinning. The population has been decreasing and the Little Blue Heron is considered threatened and of special concern in some coastal areas. (Katusic 1998, Riegner 1998)

IUCN Red List Assessment

This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). Despite the fact that the population trend appears to be decreasing, the decline is not believed to be sufficiently rapid to approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is very large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.

The little blue heron (Egretta caerulea) is a small heron. It breeds in the Gulf states of the US, through Central America and the Caribbean south to Peru and Uruguay. It is a resident breeder in most of its range, but some northern breeders migrate to the southeastern US or beyond in winter. There is post-breeding dispersal to well north of the nesting range, as far as the Canada–US border.

Contents

This species is about 60 cm (24 in) long, with a 102 cm (40 in) wingspan, and weighs 325 g (11.5 oz). It is a medium-large, long-legged heron with a long pointed blue or greyish bill with a black tip. Breeding adult birds have blue-grey plumage except for the head and neck, which are purplish and have long blue filamentous plumes. The legs and feet are dark blue. The sexes are similar. Non-breeding adults have dark blue head and neck plumage and paler legs. Young birds are all white except for dark wing tips and have dull greenish legs. They gradually acquire blue plumage as they mature.

The little blue heron's breeding habitat is sub-tropical swamps. It nests in colonies, often with other herons, usually on platforms of sticks in trees or shrubs. Three to seven light blue eggs are laid. The little blue heron stalks its prey methodically in shallow water, often running as it does so. It eats fish, frogs, crustaceans, small rodents and insects.

White little blue herons often mingle with snowy egrets. The snowy egret tolerates their presence more than little blue herons in adult plumage. These young birds actually catch more fish when in the presence of the snowy egret and also gain a measure of protection from predators when they mix into flocks of white herons. It is plausible that because of these advantages, they remain white for their first year.[2]